A reinfection is classed as someone who tests positive for COVID at least 90 days after a previous infection.

Asked exactly how many more reinfections are being caused by Omicron, the professor said it is “difficult to quantify”.

Barry Schoub, chair of the South African government’s committee on COVID vaccines, told Sky News initial signs were “good news”.

He said: “Certainly, at this stage, the news does look to be promising – the great majority of the breakthrough infection (in other words, individuals that have had infection despite vaccination) is mild.

“Our hospital surveillance is showing a little bit of an uptick but certainly nothing as dramatic as we’ve seen in the previous waves.